a chipset is essentially the brain of a motherboard. it handles the data flow, or communication, between the components. cpus are compatible with sockets, and motherboards with a certain sockets are usually available with numerous chip sets from budget entry level to higher end, offering more functionality.
also the better chip sets also tend to be on higher quality mobos so the other components tend to be superior as well. for example better chipsets offer better OCing, therefore better VRMs are on the mobos with those chipsets.
but with the 9590, thats a finicky cpu and only certain mobos can handle it. as mentioned, if possible id avoid it.